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From: elwell@osu-eddie.UUCP (Clayton M. Elwell)
Newsgroups: net.micro.mac,net.micro.amiga
Subject: Portable User Interface Library Update
Message-ID: <1115@osu-eddie.UUCP>
Date: Tue, 14-Jan-86 16:14:47 EST
Article-I.D.: osu-eddi.1115
Posted: Tue Jan 14 16:14:47 1986
Date-Received: Wed, 15-Jan-86 01:23:21 EST
Reply-To: elwell@osu-eddie.UUCP (Clayton M. Elwell)
Organization: Ohio State Univ., CIS Dept., Cols, Oh.
Lines: 50
Xref: watmath net.micro.mac:4076 net.micro.amiga:1538

The Portable User Interface Library (henceforth referred to as "PL"; I
hate typing the whole thing out) is progressing nicely.  For the curious,
I will detail the one major problem I have run into, and the solution I
came up with.  If anyone is (a) violently opposed to this approach, and
(b) able to suggest a better alternative (this is important), please send
me mail with details before I get knee-deep in code.

First, I'll define two useful terms.  A ``persistent window'' is a window
that remains on the screen until it is explicitly removed by the user.
Document windows, etc. are good examples of persistent windows.  Temporary
windows are things like alerts, modal dialogs, pop-up and pull-down menus,
etc.

Here is the problem: On multitasking systems, such as Intuition, Microsoft
Windows, Sunwindows, the Apple Lisa Office System (R.I.P.), etc., each
application has its own persistent window, while on the Mac and GEM, each
application usually has several persistent windows.  What this boils down
to is a difference in philosophy about who controls the desktop.  To
illustrate, let's imagine you have a (hypothetical) program called ``PL Paint''
which lets you edit, save, & print bitmapped pages.  If this program acted
like MacPaint and opened up three or so windows (a palette, a tool chest,
and a document window), it would work fine on a Mac, but would get confusing
real fast on a Sun or Amiga, since you could easily get confused if you were
running two instances at once.  Since that would be a reasonable thing to
do in many circumstances, that is obviously not The Right Way.

After doing (a) some deep thinking about this, and (b) a lot of playing
around with existing systems, including Sunwindows, Smalltalk-80, Xerox XDE,
Microsoft Windows, GEM, the Mac, and Interlisp-D, I have come to a conclusion.
The right way to approach the problem is to use a concept that is used in all
multitasking systems and some Mac/GEM programs.  This is the concept of a
``pane''.  A good example for Mac users is MacDraw.  Each document window
is split into several parts: the tool chest, the document, the rulers, etc.
Controls such as scroll bars can also be thought of as special-purpose
panes.

Because of the reasons mentioned above, PL will encourage the following
windowing behavior: a program should have one persistent window per open
document (or more accurately, per user context) which should be split
up into panes if necessary.  This way you get the benefits of multiple windows
without losing track of what windows are associated with which document or
application.

Comments? Suggestions? Words of Wisdom? (No religious flames please.  If
you object, defend your answer :-))
-- 
				-- Clayton Elwell
				Elwell@Ohio-State.CSNET
				Elwell%Ohio-State@CSNET-RELAY.ARPA
				...!cbosgd!osu-eddie!elwell